goinggear.com advertises an MC-E TurboHead.
The TLS TX3 head supposedly uses a standard P60-type pill, so in theory LED upgrading/swapping could be relatively easy.
If you use a netkidz tower kit, then building a tower yourself is definitely the least expensive route for an LED upgrade. Besides being less expensive than an AW tower, the netkidz tower also takes regular 17mm diam drivers, which can be gotten very cheaply from DX, KD, and others. The AW tower kit uses 14mm drivers, which are mainly available only from The Sandwich Shoppe (KD has a 14mm boost driver called the FD-A, but I have no direct experience with it). The Shoppe's drivers are first-rate, but you pay for the quality.
If you are price sensitive, a netkidz tower will cost you about $25. An XP-G R4 is about $10. A DX or KD buck driver is less than $5. Assuming you already have miscellaneous supplies like teflon wire and thermal epoxy, total materials cost is about $40. Otherwise, you'll have to make a min order from mudman cj for wire ($5 min) and buy some Arctic Alumina thermal epoxy or similar for about $8 or so. Or get the cheap Fujik thermal glue from DX for a couple of dollars.