Finding A Grant For a Disabled Child

Where can I get a grant during these difficult times??  I am supporting a family of a disabled 12yr old boy.  He has outgrown his running/cycling stroller and as his disease has progressed he also needs more support for his trunk and head.  Being able to go outdoors with his dad who jogs with him in the stroller or takes him into the countryside is such a wonderful experience for him.  He has lost the ability to speak but his vocal sounds demonstrate how much he is enjoying this experience.  We don't want him to be stuck indoors in his wheelchair so would like to secure a grant for him to get the adult stroller but it's very expensive.  The family have managed to get a grant from one small charity but they have a £1400 shortfall as the stroller is very expensive.  A lot of the grant providers eligibility criteria states they must be on benefits but the only benefit they have is DLA for their son.  Does anyone know of any charities that I could approach?  My first thought was The Family Fund but their criteria is that the family have to be on a low income and in receipt of benefits.  I hope someone can help as it would mean the world to this family if they could continue giving their son some much needed outdoor leisure experiences.  Many thanks in anticipation of your help.  I've found this site so fantastic when asking for advice and information.