This is the one I got and I really like it: IPOW Peloton Desk Tray with Cup... https://www.amazon.com/dp/B088D88FP8?ref=ppx_pop_mob_ap_share. I was also a bit put off by the prices of these trays and intended to do a DIY deal. But I chose one of the other buying options on Amazon (like slightly used, etc) and mine was much less expensive and came in perfect shape.

Edit: After typing all that I just reread the title and realized you have a Bike+. So, the one I ordered is my second one because the first one I ordered, from a different company, is for a Bike+. I still have it if you are interested.