You'll never get a match online unless you have a colour-corrected monitor. Only found CRT ones that can do that accurately enough. Thats mostly why I still run with one rather than modern flat screens. You can still buy them from a discount place in Wellingboro that clears computer equipment from corporates. Generally they'll have thousands of monitors but only usually two or three that are colour accrurate and those were well over £1k when new - £60 second hand, made for designers etc. Last three monitors I've had from them and very pleased with them. Therefore the colour chart matches my paint (5002) perfectly but for most people it will only be a vague indicator due to monitor deficiencies. However, putting names to RAL colours is very useful.
Proper colour charts are expensive - they were when I started my career in the print trade but with a colour accurate monitor you can get extremely close. Apart from that. ordering the basic chart from Rustoleum etc is the only solution unless you can get a good RAL chart from anywhere else. The best ones are those owned by professional paint spray shops. I've already put first dibs on a 28" CRT coming my way

- heaven knows what it cost new - several thousand I imagine.
Also worth noting that photos of vans in specific RAL colours won't be accurate either since few digital cameras (unless high end) render colours spot on and you don't know what kind of post-processing has been used. For that reason, none of the photos in the WIKI or in this thread should be taken as gospel - they're a rough guide at best.