The House of Marley has a 2 year limited warranty (in the USA, it may be different if your location is different) on their products
I suggest that you verify that the earphone's warranty period is still valid for your location.
If the warranty is still valid, consult the warranty statement that came with the documentation supplied with the earphones or search online for the House of Marley warranty provisions relevant to your location (click on world icon, next to magnifying glass at top right of page and select appropriate country, then search for warranty in customer support section) as to what you have to do to make a claim for a warranty repair or replacement.
If the warranty is no longer valid then perhaps you can figure out how to open the earbuds so that you can find out what type, value, size etc. rechargeable battery is being used and find a suitable replacement.
It may not be easy to open them as according to the user guide for Europe at least:
''BATTERY REPLACEMENT STATEMENT IN EUROPE
Your Voyage includes a rechargeable battery designed to last the lifetime of the product. In the unlikely event that you should require a replacement battery please contact Customer Services who will supply details of the warranty and out-of-warranty replacement battery service.''
Just wondering if they consider 2 years a "lifetime" and if lasts longer than that, you get the privilege of paying to have it fixed.