Search for "HiFive1". It will cost you around ~$100. If you want something cheaper, for around $20 there are a bunch of mini FPGA based boards available on Ali

Search for "HiFive1". It will cost you around ~$100. If you want something cheaper, for around $20 there are a bunch of mini FPGA based boards available on Aliexpress purposefully made to load into them a soft-RISC V core.