I know you said the vacuum heat sealers are too expensive but i personally say that's the only way to go. I tried buying a small handheld sealer i bought at linens and things, i think it was around 20.00. Ya it was cheap but it was sh*t.
It either sealed the bag in some spots and not in others or melted the bag straight through. I was so frustrated with it i returned it. I tried it over and over and never could get a consistent seal. I think if i had a large cookie order that needed sealing i would go insane using such a product, and likely would waste more $$ since i'd be throwing melted bags away all the time.
I ended up buying a foodsaver vacuum sealer and LOVE IT! I bought it at costco with a coupon. Not only can i use it on my cookies, i can also use it for my other food. I was so impressed by it, i could've sealed cookie bags all day.
So i think this investment is justified and well worth my sanity.