http://kellycontroller.com/dc-seriespmsep-ex-controller-kdzkdc12v-120v-c-79.html
This would be my choice + almost all the extra bells and whistles (it's not necessary)
http://kellycontroller.com/kdz4840124v-48v400apm-with-regen-p-956.html (there are brushless versions , if you go that way one day , regarding the motor). Read the descriptions and features all the way to the bottom of the page - that's how ANY offer should look like (+ some additional information at customer request). You'll know more accurately abut continuous Amp rate (get the next Amp grade up controller) , when you measure exactly , how much juice motor pulls.
I'll look later for more controllers(there are some people who makes FULLY programmable controllers , but they are in more exotic price range) and post it here (don't have the links at hand right now).
Once again , DO NOT look at Watt rating , LOOK at CONTINUOUS Amp rating for the controller , never mind where you get it. Let me explain : when somebody puts Watt rating in their offer, that usually means that they DO NOT produce that item , they are just selling it. It is much the same like when you're buying the car, and the dealer/seller starts talking about leather seats , air conditioning , or other equipment , BUT he/she knows nothing about the engine , in a sense HOW it works (what technology is implemented and what that really means) , or how ABS works or ESC (electronic stability control) or other similar stuff, and they most certainly will not talk about fuel consumption(or they will repeat stuff from the advertising brochure) or how much the maintenance will cost, and what are the parts that will brake first and often.
So , continuous Amp rating is the measure which interests you , because controller is comfortable (it's electronic components) working with that amount of current all day long (or more). Peak Amp rating is the measure of the current that controller is comfortable working with, only for few seconds (max) , after which it will shut down (if it has over current protection - like yours do) , or melt. Sellers usually just multiply PEAK Amp rating with certain potential (Volts) and get a some number in Watts (which represent electrical work , totally inaccurate btw). That number (i.e. 1500 w) , to average consumer sounds much better than REAL data , which should be like 700 w (yet again , that is misrepresentation) , which means that , if you have 36 V system on your trike - it can withstand only 19,4 Amps continuously, or less , because of thermal and resistant losses (and cheap battery operated drill can easily pull 60 Amps , for example , and you can drill with it for a long time). Also , it is VERY important to know quality of the components (which can be found in the manufacturer sheets) and HEAT dissipation and protection against overheating , which represent losses (if it runs cool for a period of time within specifications - it is a god one).
I'm fully aware that price is considerable , but it is a VERY good quality for that price (and there are some a bit more expensive
http://www.manzanitamicro.com/products?page=shop.browse&category_id=33 ).
I haven't be able to find in this thread (maybe I've missed it ?) what are requirements for your trike , range wise (accept the top speed). I strongly suggest that you think over switching to brushless motor , which is more effective , therefore , better performance and range , usually with better torque curve for similar power , compared to brushed motor (controller needs to be appropriate , that is - for brushless motors). Don't know the budget available , and that's a main thing when planning for a complete drive system.
Sorry for long post - I'm having problem to express myself in short manner in English, and I'm trying to explain complicated (extensive) things in simple manner.