1913 Erfurt ser. 2133 a O.M.D. 39 JN
Jeff Noll report in his book, page 116. Attributed to East Asia by Jeff, he might have changed his view since, but I will leave it to others to agree or disagree. On page 115 he lists a short K98 with East Asian FA, Erfurt/00 933, O.F.A1.21. Not really related, but in general I have no other related observations that really have a claim on such a possibility.
I kind of doubt 98a were used extensively in such roles. Perhaps a few did exist, but the Japanese of Australians would have taken them during WWI and survival would have been extremely low and existence today in any collectible condition is unlikely. I would think South Africans and Australians back then would have but them to work, back then they were rugged lot and probably weren't great sedentary collectors! (though Americans weren't pussies back then either... and lots of G98 and 98a survived, who can say.. - except all three countries are full of pussies and it is a miracle any of these rifles have escape Gestapo buy-back drives)