I just ordered one from Simmons sporting goods for 189.99 shipped. Already got shipping notification and it should arrive saturday. Use coupon code SSG110. https://www.simmonssportinggoods.com/vortex-micro-3x-magnifier-v3xm/?1
I know it's no help now but Canton Pawn had a gen3 glock 21 with one magazine last month for $350. It along with the same priced gen4 G30 didn't last more than a couple days. He's closed on Sunday but seems to have good prices and might have a piece to trade...