Welcome to the club! I'd just like to toss another suggestion your way, if I may: Don't overlook engines from other sources. Both of my motorized bicycles run reliably on chainsaw engines. In this forum, there are also many bikes using weed whackers, leaf blowers, and assorted other engines.
These are typically very easy to come by here secondhand, either as engines or in their normal configurations. I have no idea what the availability of these things would be for you, but be on the lookout for other non typical power plants. The DIY section here is a great resource for ideas of that nature.
Best of luck to you, whatever you decide!