I think making a fluorescent exposure unit is part of the 'fun' of alternative processes, and something everyone should do at some point. If you are not interested in making your own, there are two sources I would consider, Edwards Engineering Products, and Aristo. The Edwards products are a better value, and have more flexibility, so that would be the direction I'd go.
Due to the number of lamps in the unit and also the cover glass, I expect you will have very long exposure times on pt/pd and other iron-based printing processes. However, if you could convince them to do a 'custom' with twice the number of lamps, you may be in business. Have them remove the timer, and make sure the cover glass is removeable.
Also, you need to find out exactly what lamps they are using, as the information they have on the website is insufficient to determine if they lamps are suitable or not. "High UV spectrum" lamps is not really useful to determine the suitability of the lamps.
One thing about silk screening, I believe the materials used for this are a lot more sensitive than the average alternative process coating, so they don't need to worry about the speed of the exposure unit too much. However, with the very slow processes that most alternative process people are using, even a small reduction in the printing speed will result in a substantial increase in the exposure time required, so it is important to be acutely aware of this when selecting an exposure unit.
---Michael
Let me add one more note. Based on the cost they have listed for the replacement lamps in the FAQ, I expect these lamps are not going to be suitable for many alternative processes. That doesn't mean the unit is useless, but you might have to track down suitable UV lamps for printing. That may actually be harder than you think (or even impossible), depending on the ballasts they have installed in the unit, so be careful.