There are several types of low scope safeties that are easily installed in '98 Mauser sporter projects. The easiest to install is the left side type. These are available from all of the parts suppliers. They're pretty much a drop-in fit:
The design keeps them in-place in use, so no mods are needed, except for possibly chamfering the cocking piece (see below.) Some guys like them, but for me, I'm just used to using my right thumb. I use the Dayton Triaster Mark IIs instead. They're right side safeties, but require some mods to the shroud to keep them in-place:
When you first try put it in, it doesn't close enough for the cocking piece to slide through the shroud:
You need to cut a notch that looks something like this, about 1/8" wide in the side of the shroud:
It's important to keep the material behind the safety so that it doesn't fall out when the safety is off, so it needs to be a slot, not a flat.
I do this with a cutoff wheel in a dremel like this:
Work slowly and keep checking the fit and the safety engagement cam clears the hole in the shroud:
You're there when the cocking piece slides through the shroud without dragging on the safety:
Installed and reassembled, the safety is on in this photo:
With either of these safeties, they may not go on after they're installed. You may need to slightly chamfer the front edge of the cocking piece to get them to work. Be very careful here. I've screwed up several taking too much off. You need to fully reassemble the bolt and install it into the receiver to check your work, since the cocking piece goes farther back when the bolt is closed. Be sure the front edge of the cocking piece catch (the wedge part that entends downward on the underside) isn't worn excessively, as well.
Here's the mod you may have to make to the cocking piece:
After you get the safety to go on, check it my applying the safety, pulling the trigger, then taking the safety off. It the rifle fires, you have a very unsafe condition and have ruined your cocking piece. Fortunately they're inexpensive and plenty available, and all '98s use an interchangeable piece, so putting a Yugo on a German, a Czech on a Turk, etc, should be no problem.