FWIW, I'm another person who owns one of these enlargers. They're often paired with PCS150 light sources, which consist of an external control unit and a unit in the head that takes three halogen bulbs, each with a different filter (red, green, and blue). These can be used for color printing or for contrast control on VC paper. This is an unusual setup, but it's got certain advantages over the more conventional single light source with cyan, magenta, and yellow filters. The manuals and old ads on the Tri-One group on Yahoo go into details -- but take those documents with a grain of salt. They are ads, after all! It sounds like you've got a head with a traditional tungsten bulb in it. This will work in a more conventional way. You might luck out and find a PCS150 unit (both pieces) on eBay for a reasonable sum, but you might end up waiting a while for such a thing.
I concur with ath that you'd probably do better with a dedicated enlarger lens. If you're on an ultra-tight budget, I've got a spare Industar-96U I could send you, although postage from the USA to Namibia might be prohibitive.