I order almost all of my stampables thru Stampin' Up! - but when the memo cubes were discontinued, the search was on for more memo cubes!!! I just ordered some from Stamp On This. Its a website that has a ton of stuff like the cubes, boxes, bags, check book covers, etc...I ordered the memo cubes, mailed a check and had them in hand in about a week! This was my first experience with the company, but I'll definitely be ordering from them again. Hope this helps!
http://www.stamponthis.com/SOT-memocube.htm
~Amanda