we are using vBulletins subscription manger for the place to purchase styles .
also have a link to another copy of the file :
either :
http://gfxstyles.com/GFXStore.php or
http://gfxstyles.com/payments.php .
it is done thru paypal .
they do accept credit cards with out having an account on the bottom of the page .
a style owners forum will then be visible to down load your style and receive any support you need .