It's the ITT relay bottom as posted below the post you quoted. Markus and I posted pics.
I bought mine from this seller
Find many great new & used options and get the best deals for 6 x ITT 256ADY600Ω Multi-contact Relay - 24 volts DC 24VDC NOS at the best online prices at eBay! Free shipping for many products!
www.ebay.com
Those might be the shorter versions on the furnace which are harder to find, but the other ones cut down would be very close.