You can get N99 or N100 masks. I haven't seen any that don't have a valve for breathing out so they don't protect others, just yourself.

For masks, the convention is that the number is its ability to filter out small particles and the letter is for whether it also protects (P) against oil-based particles or not (N), with R offering partial oil protection. There's nothing wrong with using a P99 or P100 but it's probably not doing anything more than an N99 or N100 for airborne diseases.

The silicone respirators that you can hook N/P100s to can be pretty nice. They have better airflow, in my experience, but are also much heavier. You'll get a wet face using one for hours.

As others mentioned, fit is important. If you have a gap in your seal you've kind of defeated the difference between N95 and N100 already. If you have facial hair, shave. Then fit your mask to your face by adjusting the nose thing or the straps if they are adjustable. Do some rapid breaths in and out and see if there's pressure/vacuum.

Also N95 is probably enough for the vast majority of scenarios. Given that money is limited, it might be better to buy many N95s rather than fewer N99s or N100s so that you can rotate them. I keep around the higher-Ns for occasions that seem particularly risky like poorly ventilated areas packed with people.