Costs

The idea is to supply them to the drivers free of cost, this isn't a business of any description.

The only people that would make any money out of this are the local companies that supply the bamboo and sails.

How much to make them ?
Fabric Sail

The sail would represent the majority of the cost as it would need a fair bit of fabric and require sewing to create the channels for the bamboo to slide into.

A marvellous lady who knows her printed fabrics and has the facility to have them made and printed (or printed, then made) is looking into the cost to produce the sails from the same parachute-like fabric used for re-usable bags.

Bamboo Poles

2 x 2.5-3m bamboo poles, no idea of the cost, please get in touch if you know.

Fixings

Screws or tie-wraps & string or bungee cord cost from almost nothing to not very much.

Total cost per unit

Total = sail + bamboo + not a lot.

...to be updated, obviously the price would drop a good bit for bulk.

Who would pay for them ?
Benevolent folk who like ponies

Tourists, ex-pats, locals or whomever, there could be a PayPal donate button on this site.

Local businesses

Resorts, dive shops and restaurants might be keen, perhaps just for obvious pony-welfare reasons but also if they see a benefit; see branding, below.

Animal charities

Worth asking, do you have a relationship with any charities that might be interested ?

Branding

Hotels, dive shops and other businesses could sponsor them as they are, or we can arrange to have their logo printed on sails (our potential sail supplier can do this), which would up the cost but give them more reason to get involved.

Several businesses in a locality could contribute and a run of fabric be made with multiple logos printed on it, so each business had their logo a few times semi-randomly on each sail.