Here's a brand new one for starters which looks to be the same as yours (?) ... https://www.ebay.co.uk/itm/DIAL-TAG-HEUER-F1-HX0266/302649416687?hash=item46774f9bef:g:m1UAAOSwYNxagv4f . Someone else on this forum might have another source other than ebay.
However at this price it's also worth looking out for (non-working) complete watches in good condition. Assuming this is the same as yours then this sold for £41 recently as an example of what can come up if you keep an eye out: https://www.ebay.co.uk/itm/Ladies-TAG-HEUER-F1-200m-Watch-Spares-Or-Repairs-/293105389179
Perhaps one further suggestion is also to consider an alternative Heuer dial. Unless you're set on the pink there seem to be quite a lot of other Heuer dials available. Of course you'd have to double check diameter and dial feet positions but just an idea if all else fails!