These are not exactly the same ones that I use, but they will work. The cleanest adapters are the old Suntour Superbe type which adapted short-reach caliper brakes designed for 700c wheels for use on bikes with 27" wheels, though these adapters are very hard to find nowadays. If the adapters are expensive, it may be cheaper just to convert your v-brakes to the type which have longer slots. If price is no object, the Paul Motolite brakes work very well. My local shop sells the longer style v-brake arms, the entire kit, front and rear, is only $25. No special adjustments are necessary.

With the 20" wheels the fold is not as tight, though I can still fit the bike inside my Birdy carrying bag.

The 20" conversion makes an obvious difference in speed, handling, and run-down. And the larger wheels give me more clearance for my medium cage derailleur.