I am pretty sure any 89-98 tracker/sidekick manual hub will bolt right onto yours. You can probably pick up some used hubs for under $100.
What some people do is put manual lockouts on and also swap out the thirdmember that contains the air disconnect for just a regular third from the 89-98 trackicks. What that does is get rid of the air activated front diff (which some people have problems with...actually it is the air pump that people have problems with) and it also keeps the front axleshafts from spinning all the time. A thirdmember with gears will probably cost you around $150. If you decide to swap thirds, you need to make sure the sidegears are the correct spline. Yours should be 26 spline and only 96-98 thirds will have 26 spline sidegears. Or if you can't find a 96-98 third, you should be able to swap your sidegears into an earlier third. Also make sure the third you get matches the gear ratio you have, or you could also swap your gears over to the earlier third. The only ratios available in the earlier thirds are 4.30, 4.62, 5.12, 5.38 and 5.62. I am not sure what gear ratio yours will have.