ummm this doesnt really answer your specific question and i think most bags out there come with ties or drawstrings......but
when I transport my snakes I use Rubbermaid tubs with the tops...I drill holes on top and carefully clean up any spikey edges. The snakes wont get out if you buy good quality locking top tubs ( and if getting out is a concern..i duct tape the top) I found that when I bag my snakes they got stressed out...especially my Ball. In the tub...they think they are in their hide box.
A medium sized tub comfortably holds my 35lbs Boa. And the tubs have built in handles! You cant beat that!