Where to get scrap insulation foam?

[RobertInOntario]

As some of you might know, I’m thinking of expanding my small 3x5’ layout by adding a 13” wide by 3’ long section.

Since the layout is made up of insulation foam, I simply need to obtain a small piece of insulation board. I could spend $20 buying a new one of these but thought I would try doing it on the cheap first.

Does anyone have any suggestions where I might find some scrap foam board? I’m checking off and on at my local Home Depot. I guess construction sites, renovated houses, etc., might be good sources?

Thanks,
Rob