See on the triple ring, there is a set of bolts that look like yours going through the middle ring. There is a second set of bolts that hold the inner ring on, these days normally threaded into a second set of bolt holes in a triple crank.
The retro eBay set - I’m now wondering if the inner ring is bolted into extended parts of the middle ring. I haven’t seen this before to verify, it could work in your favour but not be easy to find.
Your crank has no second set of bolt holes to fit an inner ring, and I would expect it to be difficult to track down replacement rings which work like that retro set and also cost less than replacing the whole lot with an inexpensive new chainset.
That bashboard has been installed in place of the outer ring, which is unusual as you notice, the other set has it mounted to the outer ring. With an outer ring on as well, the bashboard would be flush against it and leave no room for the chain, plus obstruct the proper mounting hole for the bolt to fit in.
Finally, see how the bolts you have are recessed down into the slotted nut, whereas on the eBay example they are threaded nearly to the top of the nut. Looking from the inside. This means your bolts are already too short and are not fully engaged in the thread of the nut.
So to do the conversion you would need a new set of 3 rings, two sets of bolts and some way to modify and attach the bashguard with enough clearance for the chain. That’s if all goes well. It’s something you could look around for the parts to do it with and think about the time and money required vs buying a new or used set and swapping the whole lot.
There could be unforeseen issues like chainline, frame clearance etc. Just be careful not to throw good money after ‘bad’. (It’s not bad as such, but it’s not quite meeting your needs and the expression is almost right).