If building your own software router is too much work for you or you prefer a Hardware router there are several available
Here are a few examples of Hardware Routers with Dual Wan Support. Unfortunately these are not cheap and I doubt that they are easy to come by in South Africa, if anyone knows of local suppliers please let me know so that I can link to them.
Cyberguard SG-570
Cyberguard SG-575
Linksys RV082
Xincom XC-DPG502
My Personal favorite comes from Symantec, its not their own product they bought out Nexland who originally produced this router, since then the price has doubled however it is still a great router. Have a look here.
There are many others available, Xincom & Edimax actually make several Dual Wan Routers.
There is one router though that really takes the cake, this router can handle up to 4 WAN connections. I dont really see anyone in South Africa using a Quad-WAN router but then again you never know. Either way thanks to Edimax for pushing the limits. If you want to find out more about this beast click here
For some South African options have a look at:
Sparklan
Wifionline sells the Edimax range
ISE supplies the Hotbrick Router
For an all in one solution have a look at Dlink