For you list maniacs....

[RWS]

. . . . I don't have the right style loafer at the moment, but shall be hunting for some this summer.

I'd be interested in seeing what you choose and in learning why you chose it. It would seem that a slip-on worn with a suit should not distract by either its plainness, its over-decoration, or its novelty: a difficult set of criteria to satisfy. (I've worn -- rarely -- both tasselled and "penny" loafers with a suit but am not, for such wear, altogether pleased with either.)

[uppercase]

Well, my taste is very suspect but I shall let you know what I finally find....

...probably nothing really suitable as, indeed, a lace up is really the proper choice with suits, isn't it?

[T4phage]

I enjoy the Edward Green Wigmore casual with suits, but that's the only style I'm that casual about. Cleverley's elastic sided models are also nice.

Agree completely. I wear my side elastic apron fronts with suits.... works a treat!