Your battery may be a rare type (as compared to TH-55). Further complicating matters is whether or not there is a fresh batch available. I do hope someone gives a report on how the battery they bought turned out. I kinda stopped doing battery threads a year ago and only think that the TH-55 battery reports may still be the most recently updated.
There is one seller of TH-55 batteries here, but if you e-mail him he might give you a response on his opinion about TJ-27
Inexpensive, they were shipped fast, included the directions and screw driver/torx set needed to open up the PDAs!
While I haven't installed them yet... those SONY PDAs keep on ticking...I was very satisfied with the service and would definitely order from them again.
(I have no affiliation with them at all, just a happy customer.)