tp9 add on rails?
I have seen some pictures and it looks like they can be attached but don't see them listed on the DSA website.
instead of buying a top mounted tri rail. I would just like to add a rail on the right side since thats the side that loks like it has 2 rail holes
I know what you're talking about with those holes. But, you will probably either have to make you own rail section to fit on there or get lucky and see if some rail was already made for that spacing. I'm damn near certain that those indents are metrically spaced, and probably specifically for that gun. Maybe some HK rail section could work, I don't know.
Those indents aren't there for people to make their own, but rather for the factory to use. The top rail is the same molding if it has the rail or not. Those holes get drilled if it does. It hasn't been my experience with dsa that they are clearly aware of their own product line for the TP9 so I'm not sure if they can sell just the rail or not. I know they sell the top cover for $140 or so (expensive for what it is). They used to come with the ghost ring sights but not any more :(
I had thoughts about how common the airsoft version was (it looks like it has the exact same mold parting lines so....) but they only made a small run of MP9s and they were $275 or so.

UH60's pic isn't working for me.
Your best bet I think is going to be to buy a new topcover.
Otherwise, like new said, check the spacing between the holes and compare to an HK rail section like those that fit on the UMP or G36 handguards. B&T also makes one, BT-21731.
I looked at this on mine, and personally (not an official DSA opinion) I would not want to drill there. It is terribly close to the top. To mount a light on mine, I used a 90 degree angle mount installed very far forward on the top rail. I believe it was a Pro-mag brand accessory, but did not keep the packaging. It does not block the sights or my red dot at all, and left the bottom rail available for a front grip (mine is an SBR).
John