Setup Internet redundancy for small biz

Management would like to have redundant Internet access for incoming traffic (web/email) as well as outgoing (workstations). The network uses NAT (static for servers, dynamic for works), with translation done on the access routers. We already have 2ISP connections with 2 IP blocks.

I’ve seen various solutions on the web, but all seem to require a $2000 – $3000 hardware/software solution to route over the two lines. Is there any other way (without uing BGP)?