Many of those old samples are from typical sample-based synthesizers of the 90s. I can't really point out any specific sample sources for this specific track, but both tracker artists as well as "professional" jungle producers have used the typical hardware synths of that time (e.g. Roland JV-2080, Korg Trinity, etc...) and some well-known sample CDs. Many hardware manufacturers are releasing plugin versions of those synths these days, so you can for example get VST plugins from Roland emulating the JV-1080 (the 2080's virtually identical predecessor) or the XV-5080 (the 2080's successor, which can do anything the 2080 can do and more), or Korg's Triton (which is the successor of the Trinity). When you directly sample from these plugins they will sound a lot more hi-fi than tracker tunes or even professional productions from that era, because typically mono samples were used (with some depth added afterwards by passing them through reverb), and in the case of modules, the sample rate was often reduced as well.
You can load those plugins into OpenMPT and create the required samples directly in OpenMPT. Once you created the samples, you can go back to pure sample-based tracked in IT or XM format. Whether you want to keep the samples pristine or downsample them / convert them to mono is up to you.
If you want to look into some sample CDs, you can for example look into Polestar Magnetics or Zero-G sample CDs, stuff like Jungle Warfare, etc... I think many of them are still for sale as WAV sample packs these days.
I hope that helps!
