I just had my heads done and ended up needing to replace some of the rockers so I went ahead and replace them all.
The machine shop that I use assured me that they could get exact OEM replacement rockers.
They got me Clevite # 214-1029 (23-836) rockers and they look great, they are NOT 100% exactly like Fords, but I'd say like 97% the same.
They also had a listing for Seald Power rockers, again NOT 100% exactly the same as Ford's but again about 97% the same, the part # R-836 I do have a complete set of 16 factory original rockers in which about 8 have been determined to be in need of replacement if someone needs them.
The 289HP rockers ARE DIFFERENT than standard 289 rockers as outlined in Tony Gregory's book 4th edition on page#21