Hello poaky1,

The number for Harbor Freight is:
1-800-444-3353.

For the 6x8 greenhouse, you can buy a bag of 72 clips for $9.99, plus shipping. To save them looking it up when you call, it's the Part number 46 panel clip
and the SKU number is 27339.

If you'd like more clips, they can send you a bag of 130 clips, for $15.99, plus shipping. This is the size bag they usually sell to folks with the 10x12 greenhouse, but the clips are all the same (they just use different parts numbers.)

For the bag of 130 clips, order the Part number 53 panel clip, and give them the SKU number 29457.

Thanks Mudhouse, I will be ordering a couple replacement panels too.

You're welcome! I ordered extra clips this year, and panels year before last, and they shipped both pretty quickly.