Getting started with the components is actually a lot easier than I recalled.
In the original TA series driver thread Texas_Ace provided a link to a DigiKey shopping cart with all of the necessary components apart from the 7135s. The only item currently unavailable is a resistor and there are three alternatives available. If you’re in the US shipping isn’t expensive and it’s free for international orders over $50.
You can get 100 7135s for $12.58 shipped from FastTech, although I’m not sure whether they’re the good ones.
The 17mm TA driver PCBs are $2.25 for three.
Ordering 25 each of the ATtiny85, the Schottky diode, and the cheaper FET, 50 each of the capacitors, and 100 each of the resistors comes to $71.27 with free shipping. Add the 7135s from FastTech and 17mm boards from OSH Park and it works out to ~$4.10 each for your first 25 drivers, with lots of the inexpensive components left over for your next batch.
When I first looked into it I probably baulked at spending over 120 AUD on driver components, but these days it seems quite reasonable. I guess it just depends how far down the rabbit hole you are. It helps that I now have a decent soldering iron, hot air station, adjustable power supply etc. 
Of course, unless you’re doing the soldering for fun, you’re probably better off ordering an assembled driver from someone like Lexel or Led4power.