Radiator cap replacement.

I've lost the rad cap off my 1980 KZ1300 and am wondering if any other cap will fit. P.N. is 49085-1051.  I checked the cap on my F150 and it's not even. close. 

Using the Search Tab and searching for "radiator cap" and expanding the search for "any date" and came up with this from 3 years ago (thank you Phil)

Replacement Radiator Cap

Thanks for that, NAPA here in Canada crossed the Stant 10229 to a NAPA 703-1697 but it didn't seal. The centre part with spring needs to be deeper. I'll try a few more auto suppliers and if that fails I see a Stant on Amazon. No hurry as winter is starting in the north.

this works !

Ok Good thanks, I'm going to try to source one local but if not then I'll order that one off Amazon.

I went to another parts supplier here in Canada (PartSource) and they too matched the Stant with their own. It looked like the NAPA one and had Motorad T13 stamped on it.  I never bought it. The distance from cap bottom to the seal was 3/4 of an inch. I came home and measured the bike and it looks like the same 3/4. What am I doing wrong, the NAPA one fit loose with no seal on the bottom and as this second one looked the same I'm assuming it won't seal. Yet the rad mouth looks like 3/4 in deep.
Then on to Amazon and found the Stant 10229, it showed the Motorad 13 on it and a place for does it fit your vehicle so I entered the 1980 KZ1300 and it says No does not fit. What's going on??