There are third parties that make little rings, similar to a D-ring (I believe you can get them on
Amazon even) that make a classic speedy look like it was meant to have a strap on it. Sort of how the Alma BB handle attaches. You definitely run the risk of unevenly wearing on the bag by pulling on only two of the four pressure points on the handles, but you could probably counter this by swapping which two attachment points you use to attach the strap occasionally...I've been thinking about doing this myself with an old limited edition speedy. Can't decide if I should do that or just order a My Heritage one painted with my initials