I would think that a traditional Ebike with a solar charging station at home would be the most straightforward route... Panels with any respectable output are bulky as heck.
This way you could have a large deep cycle marine battery array with large panels oriented towards the sun as the "home base" to recharge the Ebike when yer done riding it. If it's built like a small shed it'd even give ya a place to park it out of the weather.
There's been any number of "pure" solar bikes, expensive, fragile and cumbersome - they're not really "daily drivers" although cool as all get-out.
I messed about w/solar power quite a bit and while awesome it's more than a lil picky. With separating the charging "station" from the bike you've the best of both worlds really. The bike itself won't care if it's rainy and gray out and the charging station will happily store whatever power it can gather, whenever it's available. Add on a lil wind gen and you'll look forward to bad weather too!
A heads up though, yer talking about a pretty sizable investment even if you scrounge a lot. Charge controllers aren't cheap and ofc there's used/surplus panels and whatnot - but they still aren't cheap and the batteries need to be in really good condition to get the most return from solar in particular. The upside is with a charging "station" you could use far less expensive (but very heavy & bulky) lead-acid batteries, my sailboat had a bank of eight Walmart deep cycle batteries that I got on sale for $60 each and they performed really well.
For the panels I'd shop around for a home array that someone is sellin' cause they upgraded or even put a "wanted" ad in the paper. The older tech is fine, most of the advancements has been to more output with less size - another reason to have a stationary system at home as the newer stuff is
pricey!
I got a fine array for my boat from a buddy that was upgrading his home system, old school and somewhat bulky it still kept up with my consumption rate under most circumstances (I used the batts for all power as well elect. trolling motor for docking). The "trick" to that is having as large a reserve (number/size of batteries) as possible. If it's a small bank and you've got 'em fully charged alla time yer wasting sunlight I figure
