My first Bike-Friday had H-bars and they were very comfortable.

You can buy the bars directly from Bike-Friday. Something you may not be aware of is these bars split at the stem to accomadate disassembley and packing. Which is what BFs are designed to do. No reason you cannot use them with a regular stem. Many BF owners like the H-bars so much that they equip their regular bikes with them. So it's been done before. It would probably be best to call them and tell the customer service rep what you are going to do so they can advise you properly.