It seems that whenever the SMFShop modification package was installed, the time was never taken to go into the following themes to add in a link to the forum shop:
ZFGC Kokiri (which is also used as the forum default theme, I never would have noticed this had I not switched to the Royal Blue theme)
ZFGC Goron (which, I may say, is far too pink and far too red. Perhaps getting some other earthly colors in there to shallow the tones of red down?)
ZFGC Zora Blue (naming is kind of messed up, as well, as it seems to simply be nothing more than a color edit of ZFGC Kokiri, as with the ZFGC Goron, but it has "blue" thrown into the name.)
ZFGC Midnight (in my opinion, this theme is somewhat irrelevant as it seems almost exactly like the Royal Blue theme, though I understand it is a Work in Progress)
ZFGC Kokiri (the darker one, which is, in my opinion, a better version to use than is the current default and the aforementioned ZFGC Kokiri.)
I strongly suggest getting one of your web developers to go into the theme's files and editing these links in, as (as I had mentioned before) some members, including myself, may not even realize that you have a forum shop system unless they switch to a non-standard theme; which, judging by the numbers, very few people seem to do.