Easily available with volume controls (direct to TV, not via CEC): oneforall 7935.
Various Roku clone IR remotes also offer volume buttons but hit and miss for it to work, and don't feel as nice/durable.
Rare: Roku IR remote model RC-ELIR, branded Onn (not Onn Roku TV). Second hand eBay not always available and sometimes sellers send other ones which don't work. Ask seller to confirm RC-ELIR on battery compartment.
Voice remote is easily available in North America and not too expensive, only a little more than the oneforall would be.
Outside NA availability of any Roku spares is very patchy. Best bet is Amazon.com shipped to your country (which can double the cost), or second hand via eBay (or new shipped from US, or clones from Far East).
NB: speakers won't work outside North America in any 200+V power country, they are not multivoltage (would need a building site 110v transformer to step down 230/240). There is an EU model of StreamBar (right voltage/plug and European mix of shortcut buttons). But not Streambar pro.
Not a Roku employee