Can't see a yellow one but there is a creamy white called Felicite Perpetue from David Austin.

Buff beauty is Buff apricot/yellow, Alister Stella Grey light yellow but fades to white.
Greenhills nursery have 'Amber cover' (Weeping) they say 'Highly attractive old fashioned cupped amber yellow flowers in great numbers ,green foliage, Fragrance: Slight, Height: Standard 5ft. £34.43' on line or phone 020 8144 9907

Not exactly a weeping rose but "Graham Thomas, Standard"
Available from David Austin Roses.

If you look for ground cover roses, you will find that you can buy ones that have been grafted onto standard and half standard rootstock, this will give you a weeping rose. From the selection available I think you will find a yellow variety. As suggested 'Amber Cover' is one of these.

Thanks folks, I did find one or two, but so many of the sites were very vague on some of the points, leaving doubt in my mind about if it actually WAS a standard and so on.

I found that one "Lieutenant" and didn't mind the 34quid, but rather drew the line at a further 20 quid for delivery.
BTW I asked the firm a question which, coincidentally, was answered by a "James".

Could your son be thinking of rose xanthina (canary bird?) It grows with a tough woody stem and often makes a standard with a weeping appearance.