Does anyone know what these type of angled headset bearings are called and how to work out the bearing spec. I am trying to source some replacements.

Is it an Orbit MXII FSA headset by chance or other FSA? if so UKBIKESTORE has them but £10 each IIRC – often cheaper to get a new headset!

a 45 x 36 degree angular contact bearing (iirc they are made for fsa by "TH" and are the same as cane creek

if its fsa its 45×45, if its cane creek is 36×45 degree

Erm sorry tango but I think your 45×45 is wrong – I certainly have an Orbit headset with 36 degree contact bearings!

45 45 is the z series\ orbit

All very useful info, but is this type of bearing avail from a bearing factor?

Unless you can buy them direct from TH Industies direct I think you will have to get them though a named supplier i.e. FSA/Cane Creek?