Another possibility is to get him a 4x5 view camera with at least ~450mm of bellows extension, and a 210mm or 150mm lens. I don't think anything is better than 4x5 for macro -- unless your main subject is moving, i.e. insects.
If your father is so inclined, I think this is a great approach as well. I bought a Toyo 45CX on closeout for $300 and you can easily find a used 150mm lens for under $200. That would leave enough of your budget for lens board, film holders, etc. If you absolutely have to have a roll film camera, the RB/RZ cameras are probably closest to what you want. Bellows focusing, whether MF or LF, is really great for macro. Good luck.
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