His guide harness has have D rings for a vest.

I was looking at this one for him: Service Dog Harness, Large Dog Harness Removable Neck Strap Compatible with Assistance Harness & Handle (Black, Short Version) https://www.amazon.com/dp/B07X3LQ8ZW/ref=cm_sw_r_cp_api_glt_fabc_DMT7JTYY1FWBA3G66TGH

Will have to think on some different clothes options for myself.