Check for threads on Japan here since one of the admin has gone to Japan (or is away there now) recently anyway. I think on Veglovers, there are only two admin/ a couple I think.
This thread in particular is helpful as someone has done the work for you if you have a printer or mobile device to save this JAPAN VEGAN 'PASSPORT' style of showcard image (onto) !! www.veglovers.com/talk/topic.php?id=12&page
eta, whatever method of downloading, you can take with you less the "VegLovers" logo at the top if you snip in image editing or such. Or with Scissors if you print it,
if you don't want to suggest you have amorous veggie intentions like what the two words might be interpreted as.
("VegLovers" is the name of a date site afterall but I'm sure what the admin going to japan wrote on it will fulfill the basic message you want-- writ in Japanese characters as you can see)
You can get online a more better known source of similar kind of message showcard than this but I forget where its got. but the one above is quite striking to look at to get peoples attention at least and like I say I'm it reads well
(I cannot translate it, sorry-- simply because I don't know japanese that well despite my very great interest)
Anyways, ask someone at TokyoVeg, someone there is 99% bound to know where you can get the showcard other than the VegLover one.
I got the link somewhere myself, but damn, even when being organized, information can still get misplaced on my PC.