I'm looking for commercial nano filler available products (like clay, ZnO, TiO2 etc.) for applications like Automobiles, Aerospace, Fire-retardants, Sensors etc.
The list of suppliers of nanoparticles is extremely long!
Your question is quite general, whereas the applications considered by you are very various and can imply different end-use properties (high strength and rigidity, thermal stability, barrier properties, flame resistance, electrical and optical, UV screening and antibacterial effects, or other specific characteristics) obtained at low nanofiller loadings as low as 1–5 wt.%.
The addition into polymer matrix of adequately modified nanofillers assessing 1–3D nano-dimensions (e.g., organo-modified layered silicates (OMLS), silver, zinc oxide (ZnO), graphite/graphene derivatives, carbon nanotubes (CNT), silica, polyhedral oligomeric silsesquioxanes(POSS), magnetite, etc.) is considered as an interesting approach that can lead to major improvements of polymer characteristic features (mechanical, thermal, barrier, etc.)
For more facility, I will mention some companies that can offer the NPs indicated by you:
Clays: CLOISITE: Organically modified phyllosilicates for thermoplastics (https://www.byk.com/en/additives/additives-by-name/cloisite.php )