I used to have a Siamese Mauser, one converted to .45-70. I don't recall any noticeable difference between the bolt stop/ejector than what's on other 98 Mausers.
I can't say for certain, but it is possible that a regular 98 part will work.
thanks for the replies guys... a member over of the Mauser forum gave me a link... to Numerick's they had them... their search feature is just pretty tough to use