Overstock.com certainly have a few a electric bikes, and last time I ordered from them I could pay in bitcoin (or a selection of other cryptos). I'm not aware of them changing their policies or no longer accepting crypto.

Fancy.com also accept crypto, and by the looks of things, have a few electric bikes to choose from on there as well. I have never used that site, however, so cannot vouch for it one way or another.

I'm not aware of any specialist bike shops which accept crypto though. You could always try inquiring in your local area - you never know, you might be able to convince a small independent retailer to let you pay in bitcoin.