Could you post a picture of the drum. That way, I could direct you , to look for the correct type of parallel strainer.
There are cutouts on either side of the drum that are different for the two different types of strainers. Those two are not really interchangeable but they both also existed in a longer form for the 14" drums. A short strainer for the Telstar snare drum is going to be a difficult item to find. The drums were only made from 1962 - 1967 and I would think that due to their rareness and oddity , that not that many have been disassembled, so finding one will be tricky.
However, one of the 14" versions is the same style as yours for sure and the only difference between them is the length of the throughrod, which could be removed and shortened in order to adapt it but even standard Trixon strainers in a complete form are hard to find.
Another option and not as good a one is this. Trixon also made snare drums with a standard type of strainer-----something along the lines of the Gretsch Microsensitive with adjusters on both ends but no throughrod to actuate the parallel drop. With this one you need the strainer end and the butt end. They are fashioned , similar to the tank type lugs but are very large and can be mounted onto a 5" Trixon shell and completely cover the cutouts. They also used the 26 strand wires that go completely across the head and through the snare gate for this type of strainer. I have a complete set of this type of strainer, wires and all, which I can shorten for the 13" bottom. It would work, retain the Trixonness of the drum and be expensive but then so would the correct strainer be. Be aware of these points as well. If you need all of the parallel strainer, you will need 19 parts to complete it ; one internal mechanism, 6 mounting screws,2 snarewire hangers, 2 mounting screws,1 lever knob,2 adjusting knobs,2 washers compatible with the previous,2 hanger pins, 1 set wires. All of the screws are metric and 2 of them very specific to Trixon. The other 6 will be difficult but not impossible to replace.
Regarding the wires. Trixon used 18 strand wires up until 1963 and 26 strand wires afterwards, with different corresponding hoops. The snaregate in the two otherwise identical hoops is of a different size and the 26 strand wires will not fit into the earlier hoop. I have both types of hoops, if you need one or the other.