There are some aft mkt handles, 0l0829, on ebay or try Florin Tractor 916-383-0317 for maybe nos. Try Hahn Tractor Seats for the cushions, very good quality, keep em tarped! 208-340-5084 or 208-841-0010. Cat dealer may have them too.

Ebay has the new style handles, type in caterpillar 0l0829

we were able to get clutch lever handles from the dealer for our d46u pn: l-829 which updates to 0L0829 and interchange 6F9759. the throttle and steering handles are the same. it has 1/2unf 20 thread.
and its still available in the cat parts system. 6f9759 is no longer listed.

I've bought both genuine Cat handles and aftermarket from Florin about 5 years ago, I really like Florin for parts, but their aftermarket one's are crap, mine are split and rusted before I even fitted them!! Go for genuine, they were not that expensive last time I bought some, like $30 each??

John Hahn made great seats for Cats, I've bought 4 or 5 of them over the years, unfortunately he retired and his son in law I think has taken over, I haven't heard how he is going. Lots of guys make their own seats, I've done half a dozen, buy the plywood and foam, and T nuts, cut and shape, it's not hard, just get the vinyl done by someone who knows what they are doing.

Lol, if they cant tell the diff, then.....

0L0829 is the correct designation of the handle P/No.
I believe the hex. handles were phased out in early days as I have operated a Ten or Fifteen machine of Mike Meyer's with one of these and they are not kind to your hand/fingers after some hours in the seat.
Cheers,
Eddie B.