Thanks for your interest in purchasing more - I'm reordering today and will have them up for sale as soon as they arrive. At this time they are being sold as Buy It Now items on ebay, but if you'd like to ensure you get one as soon as I have more, just hit the "email me" button on the sidebar and let me know you'd like one.
They are 8" x 10" sheets of thick red rubber (unmounted and untrimmed), pressed by Della at I Brake For Stamps , so you know they are high quality :o) They come in an acid-free clear envelope with an index sheet. Cost per sheet is $19.95 and shipping is $3.50 in a bubble envelope, sent via USPS First Class mail. I can ship to Canada for $1 more, but other out-of-the-US locations need to email me for a shipping quote. You can pay with a check, or Paypal.
If you buy a sheet I'd be happy to send you the four sample cards shown below as an email attachment so you can print them out for future reference, so just let me know if you're interested in that.