[OOL] BOOL Firewall Recommendation Needed

I am looking for a recommendation for a bridging firewall that I can use with our small business BOOL service that will pass our static IP's to systems behind the firewall and allow for port blocking. Every solution I am finding are routing firewalls that either replace the ISP router, which is not possible with BOOL, or shield your IP addresses behind NAT. I basically want the functionality of a routing firewall but in a bridging configuration. Anyone here running BOOL have such a setup they can recommend? -- I support the right to keep and arm bears.