At the high end, the standard workhorse for really serious hobbyists and rock hunters is the Ludlum Model 3 with a 44-9 pancake probe [1,2]. Throw in a scintillation probe [3] if you really want to find needles in haystacks. There are perennial bidding wars on ebay for these things surplus, but the manufacturer has a very hobbyist-friendly reputation. They've walked me through a few DIY repair jobs on ancient equipment they were under no obligation to support.

1. https://ludlums.com/products/all-products/product/model-3

2. https://ludlums.com/products/all-products/product/model-44-9

3. https://ludlums.com/products/all-products/product/model-44-1...