If it is just single CHIFI DD IEMs like the BLON, based on your requirements I would recommend you to check out:
1) TFZ No. 3 - more subbass extension and midbass quantity than the BLONs. Better technicalities (instrument separation, clarity, details, imaging) also. Soundstage and timbre slightly less good as the BLONs, but isolation is much better. It may be a bit brighter than the BLONs in the 2 - 4 kHz and 8kHz areas, but this gives it more sparkle and details than the BLON as such, so it's a tradeoff.
2) Semkarch SKC CNT1 - there's 2 filters, the gold one makes it more neutralish/brighter, whereas the black one makes it more bassy. It has better technicalities than the BLON, better fit. With black filters, the bass quantity is thereabouts, but it is faster in the bass than the BLONs. Also the lower mids are boosted relative to upper mids so male voices are more forward than female ones. But it is quite a nicely tuned set, no harsh peaks/valleys. BLON's timbre is slightly better.
3) Toneking Ninetails - has front + rear filters to give 9 tuning options, from V shaped to basshead to neutralish. On the 2nd most bassy filter config, it sounds a bit like the BLON but with better technicals, better soundstage. Isolation is weaker than BLONs. It looks weird but is actually very comfortable and well fitting. On most config options the BLON sounds to me to have more mids still than the Ninetails, so if u like the mids of the BLON, do be aware. BLON's timbre is slightly better.
4) BLON Cardinal/Bluejay - assuming u get a legit set. I think u can ask the sellers first before buying which set they have in stock. Mine is the "audition" type with no nozzles. It has similar tuning to the BLON BL-03, but with more subbass extension/quantity. Better fit/soundstage, better technicals. Stock tips/cables work fine OOTB, so no need to mess around.
If you want something pricier, do check out the Moondrop KXXS and Tanchjim Oxygen. I don't have them, but they generally have good reviews for a single DD set.
One other set that is not a single DD but that is warm and bassy like the BLON is the NiceHCK M6 (4 BA + 2 DD). Somewhat similar tonality and timbre, it has 3 tuning stock filters, but they are slightly gimicky. Definitely has better details/imaging/clarity/instrument separation than the BL-03, but might be bassier in the midbass with the default tuning nozzles.
All the best in your search!