Drayton TRV4C broken head

[Schnauzer Bites]

I have already updated this from a TRV3 using TRV4C conversion kit, including swapping over the black plastic locating ring fitted on the top of the body with the support ring included in the kit.

Now the head has broken do I need to buy another TRV4C conversion head or will a normal TRV4 head fit due to the locating ring having already been switched?

Thanks for any advice, main reason for asking being cost as TRV 4 Head is a lot cheaper.