I don't think you'll ever find a T60 bit that is shallow enough to allow even a flex handle without some modification.
I got a bit at an auto parts store that sells "Parts Master" house brand. The bit wasn't very expensive, and it came individually. It was 1/2 inch drive, and the torx insert was separate from the socket, so it could be driven out and used with a 12 mm. box wrench. Clearance was too tight to put a handle on the socket, but when I tried to use the insert alone, I pretzeled my best Craftsman 12 mm. box wrench. To start the job, I welded a cheap wrench to the 1/2 inch drive socket (the wrench size was big enough to go around the outside of the socket, leaving the drive hole open), inserted the tool into the head of the bolt, stuck a pry bar between the socket and the frame to jam it in, and used a piece of pipe to turn the cheap box wrench. That bolt was TIGHT! I had a total wrench length of at least two feet, and it took a good hard yank to get it to budge. The hole in the bolt head is rather shallow, and not very precise, either, so I strongly advise some kind of shim between wrench and frame to press it in until it begins to loosen. Once it cracked loose, I punched the torx insert out of the socket and used a 12 mm. wrench to remove it the rest of the way. Even then, I had to be careful with frame clearance at the end, and used water pump pliers on the outside of the bolt for the last couple of turns.
At some point in the past I posted a picture of the wrench in question, but I'm not at home and have neither the picture nor the link. The wrench I welded on was a cheap stamped steel one from a motorcycle tool kit. Owing to the angle everything is mounted in the engine, it helps if the wrench has an offset, and the handle should be bent inward a little toward the tip of the torx bit.
