My adult son was gifted a 95 Sentra by his FIL. The car was destined for the recycle yard, but instead dropped on my son. It ran, at times, and others prescribed a fuel pump. Six weeks after removal I was asked to reassemble it (son nearly died from a spider bite during this time).

This production has a fuel pump chamber, a coffin looking enclosure about the fuel strainer. Supposedly it snapped into a fitting inside the fuel tank. Two attempts to do so resulted in the housing detaching from the tank and free floating inside the tank. This exposes the strainer to the atmosphere and the engine starves. We can keep the tank topped off and avoid catastrophe.
I found a single YouTube video installing this design, and I believe I saw plastic mounting clips inside the tank. They were stained orange like the rest of the housing. I've spent hours online trying to identify either clips, instructions, or another design replacing this.

Am I doomed to fail? can't risk drilling. no known adhesive for that environment. Even considering very small c clamps to hold the chamber to the steel fitting/rails inside the tank. He can't invest much into it. Inflating the tires seems to double the trade-in value some days.

A 4 cylinder dragster in running straight ahead, but doomed in NASCAR

Maybe you can attach the housing or fuel reservoir to the pump itself. You are not clear as to whether the pump itself is moving around as versus the housing alone.

https://www.youtube.com/watch?v=j5JJlaKVmQk

Scrap what I said above. It seems that you are not clicking the 2 tabs into place, if they are the housing should not come loose. Look at the tabs at 5:25 in the vid and frozen. He says you have to push them DOWN and you need to verify that, if so then making a loop out of say a couple of plastic wireties one stuck in the end of another or a much longer specialty one, you'll make a loop to go around UNDER the tabs and all the way around the top of the coffin but LOOSE. Install the coffin and correctly with the wiretie flopping around. Then carefully position and pull the plastic wiretie tighter to then pull UP under the tabs. It may take some finger dexterity. If they unsnap going DOWN then UP is what will hold them in place to not come unsnapped if that is what they are doing. You want the wiretie tight but not tight enough to break the tabs off, just enough they cannot come loose because they are being held upwards. They may have relaxed over the course of years sitting in the fuel.

Done correctly it should be bulletproof. You may need to position the tie under the plastic fixture in tank rather than around the coffin and then cinch it over the top after the coffin is in place. You'll be the judge of that. If not then some other version of same idea may work.

Uh, you can drill under certain circumstances, say through the plastic if needed. New sharp drill bit stuck into the end of a small set of needlenose visegrips and pointing away from the visegrips, clamp real tight and turn the visegrips like a drill would to turn the bit and only a minute of work going through plastic.

Thanks, guys. He does low volt electric so zip ties are abundant.