I wouldn’t spend too much money on that. The keytar is a bitch to play from what i heard (never had that).
I’m selling a Korg 707 at the moment it’s a cheap plasic digital fm synth that does all the 80s sound and has the “strap-on” (sounds pornographic) option. Look for one of those 80-90s plastic synths, they are cheap and some of them had that strap option, there is some guitar like controllers out there but nowadays theyre considered “vintage” for some reason and are expensive.
Look at vintagesynth.org site and have a look aroung at what Yamaha/Korg/roland had to offer in those days i’m sure you’ll find something cheap on ebay.