Reckon you're looking at EBay or Gumtree for that kinda money Craig.
Yamaha did a sweet 3 cylinder 40V (2-stroke of course) with a substantial tiller but they still command a premium. Yamaha 50hp, we'll go luck. Nigh impossible to find now unless it's been dug out of a peat bog.
This is at Clyde Outboards, no idea of price, and now 19 years old. Probably more than your budget, but worth investigating if it can be converted to tiller.
https://www.clyde-outboard-services....remote-control