The MGA tie tack is 1-1/4" wide. This is a more common item, fairly often found at a swap meet or car show where a vendor might be selling regalia items. Not expensive, maybe around $5

Whenever these appear in public, the question is "Where did you get those?"
These MGA cowl vent pins are 1" wide. They could be used individually as tie tacks, but I like to use them on the shirt collar to help me stay ventilated and "cool". I bought these in 1989 at the MG Car Museum in Vermont, and have never seen them anywhere else.