Are you talking about short length HD DVDs that can fit on a single or DL DVD-R or are you talking about using HD DVD blank media. You can do it yourself with inexpensive software such as DVD Movie Factory 6 plus.
You cannot replicate anymore. But the larger question would be...Why would you want to? HD DVD is a dead format...if you know this, why go that route? On top of that, you would need the correct CMF image for replication. Only Sonic's and Toshiba's authoring tool did that.