The easiest solution would be to contact AgrStarts3.
Perhaps they have a permit since the plants are being propagated through tissue culture and the original plants may have been collect prior to the Endangered Species Act. Exceptions are permitted under Section 10 of the ESA. It's the ESA that prohibits interstate transportation and sales within the US.
After all the mass propagation of these plants could be argued to be conservation.
http://www.fws.gov/endangered/ESA/sec10.html
SEC. 10.
(a) PERMITS.—(1) The Secretary may permit, under such terms and conditions
as he shall prescribe—
(A) any act otherwise prohibited by section 9 for scientific purposes or to enhance
the propagation or survival of the affected species, including, but not limited
to, acts necessary for the establishment and maintenance of experimental
populations pursuant to subsection (j); or
(j) EXPERIMENTAL POPULATIONS.—(1) For purposes of this subsection, the term “experimental population” means any population (including any offspring arising solely
therefrom) authorized by the Secretary for release under paragraph (2), but only when,
34 and at such times as, the population is wholly separate geographically from
nonexperimental populations of the same species.
(2)(A) The Secretary may authorize the release (and the related transportation) of
any population (including eggs, propagules, or individuals) of an endangered species
or a threatened species outside the current range of such species if the Secretary
determines that such release will further the conservation of such species.
(B) Before authorizing the release of any population under subparagraph (A), the
Secretary shall by regulation identify the population and determine, on the basis of
the best available information, whether or not such population is essential to the
continued existence of an endangered species or a threatened species.
(C) For the purposes of this Act, each member of an experimental population shall
be treated as a threatened species; except that—
(i) solely for purposes of section 7 (other than subsection (a)(1) thereof), an
experimental population determined under subparagraph (B) to be not essential
to the continued existence of a species shall be treated, except when it occurs
in an area within the National Wildlife Refuge System or the National Park
System, as a species proposed to be listed under section 4; and
(ii) critical habitat shall not be designated under this Act for any experimental
population determined under subparagraph (B) to be not essential to the continued
existence of a species.
(3) The Secretary, with respect to populations of endangered species or threatened
species that the Secretary authorized, before the date of the enactment of this
subsection, for release in geographical areas separate from the other populations of
such species, shall determine by regulation which of such populations are an experimental
population for the purposes of this subsection and whether or not each is
essential to the continued existence of an endangered species or a threatened species.