Easy enough, the right ones are the custom molds earplugs, plugs made from and for your ear canal.

They're not cheap but they fit snugly and tight, plus they last a long time. I got mine from a recommendation from a sound tech frien. There are different kinds with filters, for example to remove the bang from a gunshot or filter out snoring but not the alarm clock or the full plug to cancel all sounds.

While taking the print for the molds I experienced total silence for the first time and enjoyed the slight tinnitus I never noticed I had.

I searched for years for the right fit in earplugs, purchasing perhaps a dozen types along the way. In hindsight I would suggest purchasing a variety pack. I think it would have saved me a lot of time and money.

Something like: http://www.earplugstore.com/foearpltrpa2.html

My personal favorites: 3M E-A-R Classic Soft Earplugs

I'm in the Netherlands - these are the right ones for me:

https://www.bol.com/nl/p/get-plugged-sleep-plugs-7-paar-oord...

I just chose the pair that dampened the most and irritated the least. These are extremely soft so it's not annoying to lie on one ear. But when they're decompressed they filter so much that the only sound I still hear are my breathing, and my long time friend mister Tinnitus. (I can distinguish​ 8 or 9 tones and pitches so my tinnitus is really heavy I guess)

I use one pair for about 1 or 2 weeks depending on how much wax is released from my ears. If the plugs get too waxy, I replace the plugs.

These aren't cheap, but they are the best imo.

I have tried about 10 different kinds and the ones that work best for me -- by about a mile -- are the 3M 1100 [1].

They have a light coating that makes them "stick" just a little bit in the ear (but not uncomfortably). This closes sound gaps that exist with other plugs and makes them way more effective.

[1] http://solutions.3m.com/wps/portal/3M/en_EU/PPE_SafetySoluti...

I'm using earplugs to sleep (and to focus) for more than 25 years now. For a long time I've used the Quies Natural Wax earplugs. Some years ago I switched to Oropax Classic earplugs. Both are made of natural wax. Wax earplugs are easy to fit in your ear and don't press against your inner ear like foam earplugs. Oropax earplugs are a bit bigger than Quies, so they don't just seal your inner ear canal but also a small part of your auricle, providing an extra buffer against sound while still being comfortable.

I use the foam earplugs from Quies.

https://www.quies.com/product/foam-earplugs/