I've talked to owners of the Yong Heng compressor and so far, the reports are good. It does work. Considering that the Yong Heng can be had for around $225, compared to the Daystate at $2000, you can buy nearly 10 Yong Hengs to a single daystate. Now, the Daystate is nicer, but if all you want is a hand pump replacement, the Yong Heng might just be the best deal.
If it's a choice of spending $225 or not getting one at all, the Yong Heng is definitely the best choice.