Tower Hobby has the NVA
Tower has had almost the entire Super Tigre line listed as Order Pending for at least a year. By the looks of things they're probably never coming back in stock. That doesn't really matter though since the only CL needle assembles they offered were for the G.34 and G.51, both of which are the short NVAs. The G.21/.35 uses the medium length spraybar, same as the G.21/.46. With the short NVA, the collet will hit the nut before the needle gets tight. The long .60 size should work with a spacer washer.
The NVA should be easy enough to find as a repro. 5-40 screws are close enough to the oddball metric originals, 5/16" for the backplate, 3/8" for the head. Gaskets can be cut by hand, but if you have to have OEM you can expand the backplate gasket search to include all the other G.21 engines and the C.35. I'd suspect the C.35 head gasket is the same, but I haven't verified that myself. The prop washer and nut should be very close to what was used up until recently on the other ST engines.
Parts for the older ST engines are hard to come by, and expensive. Ebay is probably as good a source as any, but they probably won't be cheap.