Good recommendation on where to purchase cheap, effective blank notecards and envelopes

[Todd H.]

Hi folks!

I have been getting a decent seller response with handwritten colored postcards and real stamps (4- 5% response rate) for touches 1 through 3.  For these I've been using Astrobrights 8 1/2 x 11 65lb cardstock.  However, I want to experiment and really get their attention by sending a "greeting card" style envelope for the 4th touch.  

Can anyone recommend an affordable option (online) where I can purchase similar bright colors in a bulk set that contains both a greeting and a matching envelope, particularly one that is an odd size that will stand out????

Thanks so much!!