As far as I know those type of coils are basically all the same. Either that or I've been very lucky just by using ignorance since I've used anything which would fit in the past and had success every time. Even using 4 stroke coils on 2 stroke engines and vise versa. I'm not sure which engines are plentiful over there but look for another make chainsaw coil or any other engine's coil which has relatively the same size coil. Remove it from that laminated piece if it's on one and install it on your laminated piece. As long as it fits under the flywheel and into the space it should be good. Location of the plug wire hole on the coil could be important depending on C51 saw space and how the plug wire is routed. If the square hole in the center is too large, shim it to fit tight. I have cut a layer or 2 off the laminate for fitting a smaller square hole on to one too.
If you have other engines around which would have an easier to acquire coil, check it out and try it in the C51 to see if you can use one.