You can do a sump on an aquarium without bulkheads, but it would be a lot harder to do it on one of those ponds.
Bulkheads aren't hard to do, really, and since the ponds are plastic, they'd be really easy to drill through. You can get bulkheads pretty cheap at www.glass-holes.com.
As far as pumps, the cheapest I've ever found were on craigslist or ebay. You might be able to find a decent priced pump at harbor freight, if there's one near you. You'll just want to make sure whatever pump you buy is rated for continuous use.
Another option, which isn't quite as good, would be to not filter the water. You could just add a small 500gph or so powerhead in the bottom of the ponds to keep the water moving, and add a bunch of water lettuce, hyacinth, or lotus. The plants will help filter the water, and the pumps will keep it from becoming stagnant. This would be a much cheaper option to get the enclosure ready sooner. You could always go back and add filters later.
Bulkheads aren't hard to do, really, and since the ponds are plastic, they'd be really easy to drill through. You can get bulkheads pretty cheap at www.glass-holes.com.
As far as pumps, the cheapest I've ever found were on craigslist or ebay. You might be able to find a decent priced pump at harbor freight, if there's one near you. You'll just want to make sure whatever pump you buy is rated for continuous use.
Another option, which isn't quite as good, would be to not filter the water. You could just add a small 500gph or so powerhead in the bottom of the ponds to keep the water moving, and add a bunch of water lettuce, hyacinth, or lotus. The plants will help filter the water, and the pumps will keep it from becoming stagnant. This would be a much cheaper option to get the enclosure ready sooner. You could always go back and add filters later.