I've had some luck by misusing older hardware designed for network appliances. I picked up an older Protectli Vault used on eBay for something like $65 and it's

I've had some luck by misusing older hardware designed for network appliances. I picked up an older Protectli Vault used on eBay for something like $65 and it's more capable in practice than I would've thought. (Makes sense I guess, considering it was built to do packet filtering and VPN termination all day.)