Whirlybirds decals and Whirlybits conversions are produced by Roger Evans here in the UK. I have a 2 page leaflet he sent me a couple of months ago. Contact details are
E-mail to: whirlybird@dunamai.net or rgevans@compuserve.com
Telephone +44 (0)1226 203784
Whirlybirds Decals
Christchurch Vicarage
Doncaster Road
Ardsley
Barnsley
England S71 5EF
I think he is actually a Church of England vicar who produces the Whilybird items in his spare time so production is slow and a bit erratic and usually in small quantities which is probably why retailers can't get stuff fast enough but I have had no problems dealing with him.
His list has SH-19A decals as WB72014 - £3.50 and the H-21B decals are WB72025 also at £3.50.
WBA72034 are replacement composite rotor blades for the Italeri Chinook at £6.00.
Unfortunately the 1/48 Bell 206 conversion is marked as not available at present.
Overseas postage is 10% of order value with a minimum of £1.50.
There is an alternative route. Whirlybirds seems to have a link with Heritage Aviation Models
www.heritageaviationmodelsltd.com . This fellow has a store on eBay KATANAKOLLECTABLES and most of the Whirlbirds/Whirlybits stuff is on sale there.
Hope that helps
Rod McQueen