i got one for my radiator fluid and power steering fluid from a local store. that site is the only place i can find on-line for a decent price. u can also check ebay. good luck
tuningdepot.com used to carry all three in different colored fittings for 35 each but they are not listed on their site anymore, I did email them a while ago though and they had said they were getting a shipment of them beginning of august, so maybe you have to call for em.
otherwise the site l8 listed and ebay are the cheapest, ebay has those ones engraved or embossed with mazdaspeed on em for like 55....kinda cool i guess.
You could make your own if you have the capability. I made mine and it cost me 3bucks for the fittings needed and used old scrap 3"stainless pipe and welded it.
my friend custom made ones for his srt-4 and brought it to the mazda meet. someone here saw it and did it themselves and made a how-to. I'll try to find it.