Well, not sure if this meets what you are looking for, but there are some suggestions and photos in Suggestions for mini w/o stamens showing or quilled petals?. And many of Ralph Moore's roses have an informal form, check out Sequoia Nursery.

The Patio Wonder series offered by Brad Jalbert of Select Roses are all of old fashioned bloom form. Another, called Graduation Day, also is old fashioned in bloom shape. They look like miniature Austin roses and compliment the Austins very well if used for underplanting.

Here are some pics from the www.selectroses.ca website of the Patio Wonder series. I grow all of these and have raved about them on here lots of times, in terms of winter hardiness, disease resistance, form, vigour and bloom production. Most have good scent too.

Here is Graduation Day.
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Here is White Patio Wonder.

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Here is Pink Patio Wonder.
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Here is red Patio Wonder.
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The only problem being of course...is that Brad Jalbert and Select Roses do not ship to the U.S. currently...

I don't know if they offer it anymore but Nor 'East used to sell a fragrant mauve rose with an old fashioned looked called Sachet.

You might want to look at Nostalgia. Just got her and actually put her in my OGR bed. She looks pretty happy there and right at home. There is a small area in the curve where I ususally put Short blue salvia and decided to use small roses this year that have the look of the larger roses.