What is a good PCB that you can fit with 8AWG wires?
Using your favorite Internet search engine perform a search using the keywords "pcb wire-to-board connector". You'll discover multiple companies that manufacture (e.g., Molex, AVX, TE Connectivity, etc.) and distribute/sell (Newark, Mouser, Digi-Key, etc.) wire-to-board connector products. Plan B would be to visit an electronics parts distributor website (Newark, Digi-Key, Mouser, etc.) and use the site's search tools to find the connector products they sell. You can also request a printed catalog from a parts distributor (Newark, Mouser, Digi-Key, etc.). Sometimes it's easier to find the parts you want by perusing a distributor's printed catalog versus searching the distributor's website.

For what it's worth, if wire flexibility is a concern, have you considered using multiple smaller gauge wires, rather than using a single 8 AWG wire, to deliver the 100V/40A power, where each wire carries only a portion of the 40A maximum current?  For example, if you create an eight-wire harness where each wire is the same wire gauge, then each wire carries roughly 40A/8 = 5A. Each of these eight wires can be much smaller, the mounting holes in the PCB can be smaller, the wire-to-board connectors can be smaller, etc. If you do this you'll need to be careful about how the individual wires are bundled together, encased, etc., to manage and prevent unwanted heating.