Looking for advice about "running board" add-ons to strollers

Facing the arrival of our second baby next month, we need advice about these attachments that we've seen on the backs of strollers in the NYC area. These allow an older child to ride standing up behind the new baby, functionally equivalent to a sit-and-stand stroller.

One brand sold locally for $80, another is Junior Rider Deluxe for $60. We have a Combi Savvy and were told that the Jr. would not work.

Do we have to buy a new McLaren to take advantage of one of these devices, or can we use our Combi? Any other suggestions welcomed...

[alandenisefields]

I know that Infantino sells a couple of these items---call them at 800-365-8182 to find a local dealer or to get details!
I don't know which models they work on, however.

Best wishes,
Alan & Denise Fields, Authors
BABY BARGAINS