There is electronics grade RA flux core solder but its rarely used (typically for metals that are difficult to wet) so don't worry *too* much about your boards.
FWIW, I like electronics grade RA as it works well with both new and older, oxidized parts (+ reduces consumables I need to keep on-hand).
My favorite is
Kester 1544, but Kester only offers it in large containers, while MG Chemicals offers their 835 RA in hobbyist friendly sizes (100ml or 1L). Kester 186 RMA has performance similar to an RA (I have some of this too), and there are companies and eBay sellers that break it down into hobbyist friendly sizes (
here;
Kester 951 too).
CML Supply is such a company, particularly for those in the US. They break down other products as well, such as
Kester EP256 63/37 solder paste which is the only way hobbyists/small repair shops can reasonably obtain it as Kester only packages it in 500g and 600g containers (jars & cartridges respectively). They also offer
RF741 paste flux in a smaller syringe, though Kester offers this in a 30g syringe (and as there's no metal to settle out, it's more forgiving regarding shelf life vs. solder paste). They even offer their own line of disposable pens filled with Kester products, but buying liquid is much less expensive.
CML will also ship internationally via their own website. They also do business through eBay, but they don't offer international shipping from this site.
I've also purchased from an eBay store,
Dickie's Garage Sale (i.e. buy 2 & get 1 free offers available), and it's the genuine article IME (mine uses acetone for the solvent instead of IPA, which was swapped out in 2016). $5.33 shipped for 3.75 fl. oz. would be one example of the b2g1 offer (
here), as well as smaller & larger quantities.