SPOILER: We didn't find one.
We went to garage sales and thrift stores all over the place, but we just couldn't find any desks that were cool enough and/or functional enough for either of our needs. I mean, I want a small, possibly rolltop desk for writing letters and storing stationery while Sean wants a big, executive-style desk with a wide enough top that he can keep all his electronics on it. Sounds like it wouldn't be so hard to find something that we like, but it is!
On the plus side, we did find a microwave for Seanie. He's resisted buying one for ages because he's always holding out that he'll find one for cheaper, for cheaper, for cheaper. Well, today he finally did. At one of the houses we visited, there was a microwave for $10 in a corner of an estate sale. It was old - maybe made in the early 80s? - but it will do the trick!
...and kill us with radiation in ten years, but let's not think of that.