If your train and accessories operate on DC, and the problem is an undersized power pack, a low-cost option is a laptop charger. For about $10 shipped you can get a 90 Watt DC output "brick" with a choice of plug/barrel tips. These are all recycled photos from previous OGR discussions:
Technology is such that at the power levels under discussion a DC-output power pack will be much more compact/lighter and less expensive than an AC-output power pack.
As shown in the inset above, a Universal laptop charger will typically have a slide selector switch to set the voltage. The one shown has 18V DC as an option:
On a separate note. I have no knowledge about marketing/sales of O-gauge Starter Sets and the "typical" user and their technical/wiring ability. That said, I wonder if the discussion about AC vs. DC simply causes them to head for the hills. Likewise, I wonder if the typical Starter Set user even has a pair of wire strippers or suitable wire lying around to hook up a 2nd transformer. Somewhere in this discussion is the success (or not) of the "plug-and-play" concept including from other accessory manufacturers - specifically building lights.
