In my wallet (gah I hate you americans call a purse a wallet and a handbag a purse its so confusing LOL) I found a loop thats meant to hold a ballpoint pen and my 510 slides into it perfectly. So Ive been using that as when Im out I drag my PURSE (its a handbag..) everywhere with me.
Theres also a little zipped off pocket in my handbag (stuff it Im calling it a handbag..) that also works for my 510 AND a bottle of
ejuice.
I have tried the sunglasses rope-things, but I found it got in the way swinging round my neck.