Stay with <em>I wish I were</em> or <em>if I were</em>... it's not as outdated as you'd think, and native speakers will appreciate your conscientiousness.

Older, prescriptive grammar books insist on the use of the subjunctive form "were". Most modern, descriptive grammar books accept both "were" and "was" as being grammatically acceptable, but they suggest that "I wish I were" is more appropriate in formal contexts.

i hope this will help :)

You can say either. 'Was' is now acceptable, but 'were' is more correct.

The choice is yours. Correct or not so correct? Gold medal or silver?