I recently went through this journey. Keep in mind that many of the Wiha bit options listed previously seem to be out of stock at the 'well known' retailers. Specifically I kept hearing to get the Wiha 79242 torx bit set. Maybe you can get it off ebay, but again, the source can be questionable and possibly not authentic. I ended up going with the Boker Toolkit Torx head, offered on Amazon. Also, Blade HQ has several Wiha options, which I might order extra's of at some point. Hope that helps.
Mostly I've used Wiha, but I've also used other brands with no complaints.
I started with a blue box set from Benchmade (2002 version). Despite making high quality knives their torx bits were notoriously bad (soft). But they worked fine.
Then I bought some Husky brand sets from Home Depot (mini bits inside a hollow handle driver). Those worked fine as well.
I also bought a General brand set of bits from Home Depot because the driver that came with it was of a particular design that served a specific need I had. The bits worked fine as well. The case they came in also came in handy as a travel case for my Wiha micro bits (black zippered case).
I also bought a set of Neiko brand bits because they came in a small plastic box (green box) that held several 1/4" bits securely in place and I wanted a compact bit set for travel with nothing loose rattling around. I replaced most of the Neiko bits that came in the case with mostly Wiha bits but I've used the Neikos as well and they work fine.
I mostly use Wiha because they have a wide range of sizes and you can buy individual bits.