Sorry for the late reply, Evan - problems logging back on.
There are certainly some 'universal' and 'after-market' remotes out there that will work, but you must ensure they have the same operating frequency and MUST also be 'rolling code' - or else they'll simply not work. Where you source them should make it clear that they are fully compatible with, say, the 94335E, but be aware that I've just had a quick glance at eBay and found one that claimed to be compatible but also stated in the advert body that it was 'fixed code' - so it clearly would NOT be.
Whether your new remote can also be used to control your other unit comes down to whether it's the same spec as the Liftmaster - 433.92MHz and rolling, in which case it 'should' work in theory at least.
I have a remote garage opener as well as a two-wing gate, and it is nice to have it all working from one 3-button (94335E) fob - but all my gear IS 'Liftmaster' so it should!
There are certainly some 'universal' and 'after-market' remotes out there that will work, but you must ensure they have the same operating frequency and MUST also be 'rolling code' - or else they'll simply not work. Where you source them should make it clear that they are fully compatible with, say, the 94335E, but be aware that I've just had a quick glance at eBay and found one that claimed to be compatible but also stated in the advert body that it was 'fixed code' - so it clearly would NOT be.
Whether your new remote can also be used to control your other unit comes down to whether it's the same spec as the Liftmaster - 433.92MHz and rolling, in which case it 'should' work in theory at least.
I have a remote garage opener as well as a two-wing gate, and it is nice to have it all working from one 3-button (94335E) fob - but all my gear IS 'Liftmaster' so it should!