For enclosures, Communica stocks the standard Hammond 1590B and 1590BB, where Mantech does not.
RSE also has the Hammonds at a much higher price, but also their own "RS" enclosures at VERY reasonable prices.
For 3pdt switch, Mantech stocks at about R40.
I prefer to order mine off eBay as WAY cheaper (R20) and they have bigger solder lugs compared to Mantech's.
But then there's a 2/3 week waiting period.
For components, I get everything else from Mantech as its MUCH cheaper then RSE and Communica often doesn't have specific components. For the hard to find components, RSE does have everything under the sun though, and the delivery is cool to.
Hope that helps