Hi decuevas,
If the Sleep on Latex 100% natural firm Dunlop core is 5.9 lb/ft3 or 95 kg/m3 then it’s probably a little firmer than 44 ILD (see post #2 here).
With a quick look through the DIY components list here …
diynaturalbedding sells “hard” 3" 100% natural Dunlop latex layers here which is rated at 5.92 kg/m3 and 43 - 48 ILD
ADMIN NOTE:Removed 404 page link | Archived Footprint: diynaturalbedding.com/product/3-natural-latex-slab/
Latextoppers on eBay sells a 5.92 lb/ft3 6" 100% natural Dunlop core here which is rated between 45 - 49 ILD.
Both of these are 95 kg/m3 so they would be a similar firmness to Sleep on Latex if it’s also 95 kg/m3
Latex toppers on eBay also sells a 6" organic Dunlop core here which is rated at 45+ ILD.
Foam Order also sells 100% natural Dunlop toppers here and the firmest is rated at 58 - 64 ILD but this seems unusually firm and I don’t know the density (which you could check to see if it would reasonably equate to the the ILD they list).
Phoenix