Wow!
For starters introduce your husband to the concept of "everyday sexism" seeing as it seems to have passed him by!
Secondly - I'd honestly be complaining to the shop's management/hq if a chain because that assistants attitude needs serious adjustment! Especially as it's losing them business!
As a consumer I will recommend those companies who give good service - and I think it's also natural to advise others NOT to use the ones that give poor service.
Iirc there's a stat on that, customers are more likely to be public and vocal about poor service than they are on good service.
Go all Pretty Woman on him and ride your new bike past the store, and say "big mistake." love this idea 
Thanks to my parents rightly thinking that both sexes need a good practical education in life skills my sister and I are both very good on cars and car maintenance and brother on clothing repairs and cooking and baking etc we've ALL had experiences where retail staff have made assumptions based on our sex that meant they tried to pull the wool over our eyes!
Similar to many pps when I've been at car show rooms or garage mechanics with now exh in the past, they talked to or asked him various questions...he's totally clueless when it comes to cars!
I've a relative who is not only expert on cars generally but has been an amateur racer in the past, she's had some crackers idiot mechanics have come out with! Very my cousin vinny!
I am still seething about a John Lewis assistant who spoke over my head to DH about my maternity bras, ffs. I was in a wheelchair. She wouldn't look at me.
Jesus! I'm not surprised what appalling ableism! I hope you do complain
I have a disability too but currently "invisible" so it's mainly people telling me I'm not entitled to use disabled loos! But I had to have an op a while back that meant I was temporarily wheelchair bound and yes lots of people talking over me to who was wheeling the chair, talking to me very slowly and carefully and loudly as if I were stupid or deaf or both, and people MOVING me without asking! Often putting me at risk of further injury!
I also have an extremely wealthy friend who is into gardening etc so is often in "scruff order" he generally is quite oblivious but he's had a few experiences of retail assistants being snobby towards him assuming he's poor, he could probably buy the entire shop chain if he wanted! He generally doesn't bother too much if people are off to him, but he gets very annoyed if he witnesses same happening to others and has stepped in on occasion to give the snobby retailer concerned a right showing up! Admittedly sometimes by feigning being related to the person being disparaged, flashing the cash and then saying something like "come on aunty Mary we'll shop somewhere else" at which point retailer often becomes fawning mess! Especially if it's an area of retail that's commission based!
I even remember being a waitress and a colleague being snotty about one of our regular customers because she wore ill fitting, in poor repair clothes and constantly talked about her beloved cats...
This customer was actually the local baroness and very switched on and noticed how people treated her...
She was also VERY generous with the tips she gave when visiting us around Christmas time, and around her birthday, and her late husbands birthday and she knew which tables were waited on by which staff and she NEVER sat at one of this colleagues tables...more fool that colleague.
She was a lovely lady - not just because of the tips - but just generally friendly and sweet to the staff and other customers.