I believe Addgene send strains as bacterial stabs.
This is the protocol from Qiagen.
E. coli strains can also be stored for up to 1 year as stabs in soft
agar. Stab cultures are used to transport or send bacterial strains to
other labs. Prepare stab cultures as follows:
Prepare and autoclave LB agar (standard LB medium containing 0.7% agar) as described in the last issue of QIAGEN News (1).
Cool the LB agar to below 50°C (when you can hold it comfortably) and add the appropriate antibiotic(s). While the agar is still liquid,
add 1 ml agar to a 2-ml screw-cap vial under sterile conditions, then
leave to solidify.
Vials of agar can be prepared in batches and stored at room
temperature until required.
- Using a sterile straight wire, pick a single colony from a freshly streaked plate and stab it deep down into the soft agar several times
￼￼￼￼￼￼￼￼￼4. Incubate the vial at 37°C for 8–12 h leaving the cap
- Seal the vial tightly and store in the dark, preferably at 4°C.
When recovering a stored strain, it is advisable to check the
antibiotic markers by streaking the strain onto a selective plate.
I believe if the shipping is <24hrs you could send a stab in ice.
Hope that helps