I think I've only seen bare root Siberians for sale at CostCo.

Fall planting and lots of water the first year. Full sun. I think it's easiest to add bonemeal to the planting hole.

Many reliable sources but I can vouch for Aitken's.

I have found Siberian Iris at local garden centers. I enjoyed those but wanted more variety. This spring I ordered more from Joe Pye Weed's Garden. They have quite an assortment. The plants are small but seem to be growing well despite a horrible first year weather wise.

My first planting is now 3 years old. They have become thick round clumps about 3' wide. The clumps are almost perfect circles and look like ornamental grasses.

I give them little care because my soil is reasonably rich and acid. They received a good deal of water the first year. I mulch heavily.

Original planting in second season.

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I will be happy to dig & send you what you need if you pay the postage.

Siberian iris are really easy, if they are planted in full or nearly full sun, and moderately moist soil. When the clumps beome dough-nut shaped and congested, they need to be divided. This can be done in early spring or fall. Water well until new plantings become established. In too much shade or if overcrowded, they will not flower at all.

I wouldn't describe sib iris as needing moist soil. I have several clumps that do not get that much moisture. We aren't in a dry zone, but we have a dry spell every summer and my iris grow and bloom just fine.