It sounds like you're looking for a replacement laptop charger for a Lenovo/IBM laptop with specific voltage and amperage ratings: 20V and 4.5A. These specs suggest a standard Lenovo laptop charger, often used for models with higher power requirements like ThinkPad series or some gaming laptops.

Here are a few steps you can follow to find the right charger:

1. Check Model Compatibility

• Double-check your laptop’s model number and ensure it's compatible with a 20V 4.5A charger. The amperage (4.5A) is important for ensuring the charger can supply enough current for your laptop’s power demands.
• If you’re unsure about the model, you can find the laptop's model number on a sticker located on the bottom of the laptop or in the battery compartment.

2. Ensure Correct Connector Type

• Lenovo/IBM laptops often have specific connector types (round barrel connector or USB-C for some newer models). Make sure the plug that connects to yor laptop matches the one on the charger you're considering.
• For example, older Lenovo models may have a round 7.9mm barrel connector, while newer models may use USB-C for charging.

3. Third-Party Chargers

• If you're not set on getting an official Lenovo charger, there are third-party options from brands like Anker, Targus, or Innergie that provide compatible replacements. Always ensure that the third-party charger provides the correct voltage (20V) and amperage (4.5A) and is well-reviewed.