In case anyone else is on the hunt, I just picked up my welcome/schedule sign from Walgreens for $18. It's a 20x30 poster board with a 50% off photo coupon. : r/Weddingsunder10k
Foam Core Backing Board 3/8 White 20x30- 100 Pack. Many Sizes Available. Acid Free Buffered Craft Poster Board for Signs, Presentations, School, Office and Art Projects , Foam Poster Board - valleyresorts.co.uk