Short answer — buy from established lifting-equipment suppliers that sell OSHA/ASME-compliant slings and provide engineering/technical support, inspection/certification, and training. Good U.S. sources:

• Lift‑All — full range of web, round, wire and chain slings; states products meet/exceed OSHA and ASME and offers on‑site sling inspection and sling‑safety seminars / factory technical support. (lift-all.com)

• Slingmax — manufacturer of synthetic slings/roundslings with ISO‑audited quality, extensive technical library, testing and dealer network that provides engineering/technical support. (Slingmax.com)

• Liftex (Liftex/Liftex Slings) — manufactures web/roundslings and states products meet or exceed OSHA, WSTDA and ASME standards; provides lifting/safety resources. (Liftex.com)

• Grainger (industrial supply distributor) — stocks chain, wire rope and web slings from multiple OEMs, shows rated capacities and safety/spec filters, and can arrange custom assemblies and certified products. Grainger also sells inspection/maintenance services at some locations. (safety.Grainger.com)

• McMaster‑Carr — large catalog of web/chain/wire slings with filters for OSHA/ASME and product datasheets; good for smaller purchases, quick delivery and clear capacity/spec info. (mcmaster.com)

Additional reputable OEMs / brands to consider (carry engineered products and documentation): Peerless, Gunnebo, Crosby, and Slingmax dealers — these companies publish tech specs, WLLs, proof‑test and traceability info and have dealer engineering support. (peerlesschain.com)

What to ask/require when you buy (so the sling is OSHA‑compliant and supported):

• Manufacturer’s rated Working Load Limit (WLL) and marked ID tag on the sling (OSHA requires legible markings). (lift-all.com)
• Compliance statements / datasheets showing compliance with OSHA 1910.184 and ASME B30.9 (or WSTDA for web slings). (Liftex.com)
• Traceability / test certificates and proof‑load or break test reports (when required for critical lifts). (Slingmax.com)
• Engineering assistance: ask the vendor for a lift‑plan review, sling selection (type, capacity, number of legs, angles), edge protection recommendations, and a torque/angle capacity calculation. Vendors above advertise technical libraries, on‑site seminars, or dealer engineering support. (lift-all.com)
• Inspection and recertification services (annual competent‑person inspections required by OSHA). Many manufacturers/distributors offer inspection programs. (lift-all.com)

Practical next steps (fast):

1. Determine the load weight(s), lift points, hitch type (vertical, basket, choker), environment (heat, chemicals, sharp edges), and desired sling type (web, round, wire, chain).
2. Contact one or more of the vendors above (Lift‑All, Slingmax, Liftex, Grainger, McMaster) and request a written recommendation/quotation that includes engineering calculations, proof/test certificates and lead time. Use their “technical support,” “safety seminar,” or “engineering” contacts. (lift-all.com)

If you want, I can:

• give a short checklist/email template you can send to vendors requesting engineering support and certificates; or
• compare 3 specific vendor quotes if you paste the load details (weight, lift geometry, environment).